Labyrinth shielding for master-slave manipulator



Dec. 2, 1969 c. E. JENNRICH ET A].

Filed Feb. 21. 1966 A rv-omws w k 5A m vffl W W TR 55 LT. N Q2 UnitedStates Patent US. Cl. 250-108 7 Claims ABSTRACT OF THE DISCLOSURE Ashielding system for protection against radiation for the horizontaltubular support of a remote-control masterslave manipulator. The systemcomprises a plurality of at least two spaced apart barrier walls ofradiation absorptive material tightly fitted within the tubular support.These barrier walls are penetrated by slots for passage of the tie rods,tapes and/ or cables by which motion is transmitted from the master armto the slave arm. The slots in one barrier wall are offset with respectto the corresponding slots in another barrier wall so as to be out ofalignment so that no straight line radiation path exists through thehorizontal support.

This invention relates to shielding for the interior of the horizontalsupport or through tube of through-thewall remote-control master-slavemanipulators. Such master-slave manipulators comprise generally a masterarm and a slave arm, each pivotally connected to one of the oppositeends of a generally horizontal tubular support which extends through agenerally vertical shielding wall. The through tube is mounted in asleeve or tube set in the wall so as to permit rotation of the throughtube about its longitudinal axis with resulting transmission ofside-to-side or X motion from the master arm to the slave arm. Typicalof such manipulators are those shown in Jelatis et al. United StatesPatents No. 2,888,154 issued May 29, 1959 and No. 3,139,990 issued July7, 1964.

The most common use of such manipulators is in the handling ofradioactive materials in a dangerous area on one side of a barrier wallfrom a safe area on the opposite side of that wall where the operator ispositioned. The hazardous rays and particles emitted from such dangeroussubstances as may be handled with the manipulator tend to travel alongstraight line paths of varying length. In order to prevent endangeringof personnel due to the escape of harmful radioactive products, such asgamma radiation, through the opening in the barrier wall through whichthe manipulator extends, pains must be taken to minimize or eliminateany straight line path by which harmful radiation can escape to the safeside of the barrier wall.

The present invention is directed to a shielding system for the interiorof the through tube and, in most instances, this interior shielding willbe used in conjunction with a shielding system for the annular spacebetween the manipulator through tube and the opening through the barrierwall in which that through tube fits, as described and claimed incopending application Ser. No. 529,058, filed Feb. 21, 1966. Theinvention of that application in turn relates to shielding in theannular space between the through tube and wall opening when the throughtube is supported on truck mounts as described and claimed in copendingapplication Ser. No. 529,057, filed Feb. 21, 1966, now Patent No.3,410,418.

The invention is illustrated by the accompanying drawing in which thesame numerals refer to corresponding parts and in which:

FIGURE 1 is an elevation, partly in section, along a vertical planeextending along the longitudinal axis showing a through tube of amaster-slave manipulator mounted in a barrier wall and utilizing rollertruck mounts and annular shielding and utilizing interior layrinthshielding according to the present invention;

FIGURE 2 is a section on the line 22 of FIGURE 1 and in the direction ofthe arrows;

FIGURE 3 is a section on the line 3-3 of FIGURE 1 and in the directionof the arrows;

FIGURE 4 is a section on the line 4-4 of FIGURE 1 and in the directionof the arrows; and

FIGURE 5 is a fragmentary perspective view showing connection of tierods.

Referring now to the drawing and particularly to FIG- URE 1, there isshown the horizontal support or through tube 10 of a remote controlmaster-slave manipulator. The through tube 10 extends through aprotective shielding or barrier wall 11 which is of substantialthickness. The opening for passage of the through tube through wall 11is ordinarily fitted with a tube or sleeve 12. In the configurationillustrated, through tube 10 is supported within sleeve 12 by a masterroller truck mount assembly 13 at one end and a slave roller truck mountassembly 14 at the other end. The structure of the roller truck mountsis described and claimed in detail in the copending application referredto above. The roller truck mounts per se form no part of the presentinvention. The through tube 10 is supported for rotation about itslongitudinal axis by means of a plurality of generally transverselyextending rollers 15 journalled for rotation and mounted in the oppositeedge faces of the rings which form the bodies of the roller truckmounts.

An annular space 16 exists between the inner wall surface of sleeve 12and the outer wall surface of through tube 10. Within this space areinstalled annular shielding in assemblies of two general types asdescribed and claimed in the aforesaid copending application. Annularshielding assembly 17 is an inside diameter assembly fitted with a tightfit against the outer periphery of through tube 10 but with clearancewith respect to the inner periphery of sleeve 12. The other of theseannular shielding assemblies 18 is an outside diameter assembly fittedwith a tight sealing fit against the inner periphery of sleeve 12 butwith clearance relative to through tube 10. Shielding assembly 18 isstationary and the through tube rotates within it. The shieldingassembly 17 rotates with the through tube. It will be seen that theseshielding assemblies define a labyrinthine passage through the annularspace through which substances cannot pass in a straight line.

The labyrinth shielding according to the present invention fits withinthrough tube 10. It is composed of at least two circular assemblies oftwo different general types indicated at 19 and 20, respectively. Theassemblies are spaced apart longitudinally and extend transverse to thelongitudinal axis of tube 10. Each of the assemblies is desirably alaminated structure composed of a plurality of segments in face-to-faceabutment. The segments are composed of radioactive absorptive materialand are assembled to make up the required thickness to give the desiredprotection. Typically each segment is about one inch thick and eachshielding assembly is composed of from one to six segments. The mostcommon of these absorptive materials for gamma ray shielding are leadand lead based alloys, such as lead-antimony, lead-tin, etc. Materialsof large hydrogen content like synthetic resins, such as polyethylene,and waxes such as paraffin and the like, may also be used for moreeffective shielding of neutron emissions. The edges of the assembliesfit in close engagement with the inside wall of tube 10.

As is well understood in the manipulator art, the back and forth or Ymotion of the master arm toward and away from the barrier wall 11 istransmitted to the slave arm by means of tie rod assemblies 21. As hereillustrated, each tie rod assembly 21 comprises a single rod 22 at theslave end joined through a fitting 23 to a parallel pair of rods 24extending to the master end. This avoids the necessity for providing alongitudinal straight line passage for the tie rods. Instead, passagefor the tie rods through the shielding assemblies is provided by meansof vertical slots 25 in assembly 20 for passage of single tie rods 22and spaced parallel vertical off-set slots 26 in assembly 19 for doubletie rods 24. It will be noted that slots 25 are in the top and bottomedges of the shielding assembly 20 and are aligned generally with thevertical center line plane when the through tube is in its normalat-rest position. Slots 26 are also in the top and bottom edges ofassembly 19 and are spaced on either side of that same vertical centerline plane by a total distance which is greater than the width of slot25. In this manner it is insured that the slots are off-set from oneanother sufliciently to eliminate any direct straight line passagethrough the through tube along the paths of the tie rod assemblies. Atthe same time there is no intereference by the shielding members withmovement of the tie rod assemblies and transmission of Y motion.

Other motions are transmitted from the master arm of the manipulator tothe slave arm by means of linear motion transmission members 27, such astapes and cables, passing through the horizontal through tube 10, as iswell known in the art. These motions include movement of the arms alongtheir own longitudinal axes of Z motion, actuation of the tong memberson the end of the slave arm in response to actuation of the handle onthe end of the master arm and rotation of the tong means about each ofthree axes in response to corresponding rotation of the handle. Toprovide for movement of flexible linear motion transmission members 27,either tapes or cables, through the shielding assemblies 19 and 20,there are provided relatively narrow longitudinal slots 28 and 29,respectively.

Slots 28 and 29 are disposed generally along the horizontal center lineplane of the shielding assemblies when the through tube is at its normalat-rest position. Each slot 28 and 29 has a depth extending all of theway through the shielding assembly, a length suflicient to carry therequired number of linear motion transmission members 27 and a widthsuflicient to permit the free passage of those members through theshielding assemblies without binding. Typically the length may be about4 inches and the width about A; to /8 inch.

To facilitate free movement of the tapes and cables slots 28 and 29 aredesirably aligned with one another and with the edges of the pulleys onthe master and slave arms by which they are guided into the throughtube. The slots 28 and 29 have relatively small cross-sectional areacompared with the cross-sectional area of tube 10, and they are spacedapart longitudinally by a relatively great distance. Any hazardous rayor emitted particle whose path of travel is precisely aligned with theslots will pass through the tube 10. However, even though the slots 28and 29 may be in precise alignment, the operator at the master slave endof the through tube is relatively safe from exposure to dangerousradioactive products, because the predominant portion of thecross-sectional area of the through tube is thoroughly shielded toprevent straight line transmission of harmful radioactive products.

Where the utmost in safety is desired, one of the inside shieldingassemblies, indicated generally at 19A, is provided with a slot 28A forpassage of the tapes and cables which is olfset vertically with respectto slots 28 and 29 by a distance greater than the width of the slotopenings. Assembly 19A is similar in all respects to assembly 19 exceptfor the location of slot 28A. In order to permit free passage of thetapes and cables through the off-set slot 28A without binding, means areprovided for altering the path of travel of the members 27, guiding themthrough the olf-set slot and returning them to their normal path.

These guide means 30 are secured to the inside Wall of the tube 10 andinclude a frame or bracket 31 which is bifurcated to support a pair ofparallel shafts 32 on which are journalled a plurality of pulleys 33,each adapted to carry a tape or pulley. The banks of pulleys 33 aredisposed so that the guiding tracks of one bank are tangent to a planeextending through the normal slots 28 and 29 and the opposite guidingtracks of the adjacent pulley bank are tangent to a parallel planeextending through off-set slot 28A. One set of guide means is disposedon each side of the shielding assembly with the off-set slot. It will bereadily seen in FIGURE 1 that the linear motion transmission members 27are diverted from their normal path through the off-set slot 28A andback to the normal path while insuring free passage of these membersthrough the through tube. Any chance radioactive particle which findsits way through slot 29 in shielding assembly 20 will as it travelsalong its straight line path be absorbed by the shielding assembly 19A.

The positions of the segments comprising the shielding assemblies can bemaintained with respect to one another by any conventional means. Forexample, the inside surface of through tube 10 may be provided with keysand the shielding segments with corresponding keyways, or the segmentsmay be screwed to the through tube or the like.

What is claimed is:

1. A labyrinthine radiation shielding system for the interior of thehorizontal tubular support of a remote-control master-slave manipulatorin which Y motion is transmitted through tie rod assemblies, saidshielding system comprising:

(A) at least two longitudinally spaced apart shielding assembliesdisposed in the horizontal tubular support of a manipulator,

(B) said shielding assemblies (1) extending transverse to thelongitudinal axis of said tubular support,

(2) being composed essentially of a radiation absorptive material, and

(3) fitted in close engagement with the interior wall of said tubularsupport,

(C) one of said assemblies being provided with a central verticallyextending radial slot for passage of a tie rod,

(D) another of said assemblies being provided with a pair of parallelvertically extending slots for passage of a pair of tie rods, said slotsbeing spaced apart laterally on opposite sides of a plane extendingthrough said first slot passage by a distance greater than the width ofsaid first passage, and

(E) each of said assemblies being provided with a relatively narrowhorizontal slot for passage of linear motion transmission elementstherethrough.

2. A shielding system according to claim 1 further characterized in thatsaid shielding assemblies are each provided with vertically aligned andvertically spaced apart slots for passage of rods extending inwardlyfrom the top and bottom edges, respectively, of said assemblies.

3. A shielding system according to claim 1 further characterized in thatsaid assemblies are composed of a plurality of fiat slab-like segmentsdisposed in abutting face-to-face relation and composed essentially of aradiation absorptive material.

4. A shielding system according to claim 1 further characterized in thateach of said assemblies ranges from about one to six inches inthickness.

5. A shielding system according to claim 1 further characterized in thatat least one of said horizontal slots is disposed generally along thehorizontal center line plane.

6. A shielding system according to claim 5 further characterized in thatat least another one of said horizontal slots is disposed in a planeparallel to but off-set vertically from the horizontal center line planewhereby said slots are out of alignment and guide means are provided 5to direct linear motion transmission elements in their paths throughsaid slots.

7. A shielding system according to claim 6 further characterized in thatsaid guide means comprises a pair of banks of pulleys disposed on eachside of said shielding assembly with off-set horizontal slot, said banksof pulleys being journalled on pairs of parallel horizontal shaftssupported from the Walls of the horizontal tubular supports, saidoil-set horizontal slots being spaced apart vertically a distancegreater than the vertical opening of said slots, said pulley banks beingdisposed between the horizontal planes extending through said horizontalslots with their guiding faces generally tangential to said planes.

3/1966 Bowyer.

RALPH G. NILSON, Primary Examiner A. B. CROFT, Assistant Examiner US.Cl. X.R.

